78115021 has 2 divisors, whose sum is σ = 78115022. Its totient is φ = 78115020.

The previous prime is 78115019. The next prime is 78115027. The reversal of 78115021 is 12051187.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39501225 + 38613796 = 6285^2 + 6214^2 .

It is a cyclic number.

It is not a de Polignac number, because 78115021 - 2¹ = 78115019 is a prime.

It is a super-2 number, since 2×78115021² = 12203913011660882, which contains 22 as substring.

Together with 78115019, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78115027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39057510 + 39057511.

It is an arithmetic number, because the mean of its divisors is an integer number (39057511).

Almost surely, 2^78115021 is an apocalyptic number.

It is an amenable number.

78115021 is a deficient number, since it is larger than the sum of its proper divisors (1).

78115021 is an equidigital number, since it uses as much as digits as its factorization.

78115021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 560, while the sum is 25.

The square root of 78115021 is about 8838.2702493192. The cubic root of 78115021 is about 427.4757844542.

The spelling of 78115021 in words is "seventy-eight million, one hundred fifteen thousand, twenty-one".